Perovskite Co-free La_0.6Sr_0.4M_0.2Fe_0.8O_{3- δ} (M = Cr or Ti) mixed-conductors: Preparation and characterization

The new Co-free La_0.6Sr_0.4M_0.2Fe_0.8O_{3- δ} (M = Cr or Ti) perovskite oxides have been successfully synthesized by the citrate acid complexing method. The La_0.6Sr_0.4Co_0.2Fe_0.8O_{3- δ} and as-synthesized Co-substituted La_0.6Sr_0.4M_0.2Fe_0.8O_{3- δ} (M = Cr or Ti) oxides all possess the rhombohedral perovskite-type structure. The structural stability, chemical reduction-tolerance ability (in a flowing 10% H₂/helium stream) and sintering performance of the as-synthesized La_0.6Sr_0.4M_0.2Fe_0.8O_{3- δ} (M = Cr or Ti) oxides were studied by XRD, TGA/DSC and SEM. The results demonstrate the reduction-tolerance ability of the as-synthesized Co-free La_0.6Sr_0.4M_0.2Fe_0.8O_{3- δ} (M = Cr or Ti) oxides is improved significantly compared to that of the Co-containing La_0.6Sr_0.4M_0.2Fe_0.8O_{3- δ} (M = Co) oxide. The presence of Cr^3+/4+ or Ti^3+/4+ ions in the B-sites of the perovskite-type structure can further stabilize the neighboring oxygen octahedral (BO₆) due to the stronger columbic attraction, leading to the enhanced stability of the as-synthesized Cr- or Ti-substituting perovskite Co-free oxides.